The use of turbochargers in internal combustion engines is well known. Turbochargers increase the mass of air supplied to the engine thereby enabling the increase of the power output of the engine. In addition, the efficiency of the engine is increased by the turbocharger's utilization of the thermal energy contained in the engine's exhaust gases.
Turbochargers typically have a turbine wheel connected by a rotatable shaft to a compressor wheel. The turbine wheel is contained within a turbine housing and is driven at speeds of up to 200,000 r.p.m. by engine exhaust gases. The turbine wheel operates at a relatively high temperature. The common shaft in turn drives the compressor wheel at a similar speed, forcing air into the engine. The compressor wheel is contained within a compressor housing, and the compressor wheel typically operates at a lower temperature than the turbine wheel.
The shaft is lubricated along its length between the compressor wheel and the turbine wheel. The portion of the shaft between the compressor wheel and the turbine wheel is contained within a bearing housing. Shaft is rotatably connected to center housing via bearings contained within bearing housings. Seals are used around the shaft, both to prevent leakage of oil from the bearing housing into the compressor housing and turbine housing and to prevent leakage of gases from the compressor housing and turbine housing into the bearing housing. If oil leaks from the bearing housing into the compressor housing or turbine housing, unwanted emissions will likely result from the engine, including oil or black smoke. On the other hand, if exhaust gases leak from the turbine housing into the bearing housing, known as “blowby,” the exhaust gases may contaminate the oil, therefore reducing the oil's ability to cool the engine and necessitating early replacement of the oil. Also, blowby can have detrimental effect on the sealing of a crankcase of the engine and on a crankcase closed-circuit ventilation system.
Due to the high temperature of the turbine wheel, turbine housing seals must be able to operate effectively at high temperatures. It has become more difficult for seals to effectively seal the turbine housings of today's engines due to the recent drive by engine manufacturers to create higher-powered, more efficient engines. This drive has resulted in higher engine exhaust temperatures and, therefore, higher temperatures within turbine housings. Because of the temperatures and speeds involved, rubber seals do not effectively seal turbine housings.
One type of seal that is commonly used to prevent blowby and oil leakage employs metal sealing rings similar to the piston ring seals used between pistons and cylinders of engines. With such seals, a metal ring of substantially square or rectangular cross-section is fitted into a similarly shaped annular groove in the rotating shaft. Although this type of seal generally works well, allowance has to be made for a certain amount of misalignment, and accordingly, a clearance between the metal ring seal and the groove must be factored into the seal dimensions. Therefore, the seal is not optimally connected to the shaft. There is also a radial split or gap in the ring, reducing the effectiveness of the seal. In addition, to use such a seal, a groove must be manufactured into the shaft. This manufacturing process adds time and expense to the overall turbocharger manufacturing process.
Another type of turbocharger seal is disclosed in international patent application # WO 91/03626, published on Mar. 21, 1991. This seal has a annular seal connected to an elastic diaphragm. The annular seal surrounds the shaft, and the elastic diaphragm urges the seal into contact with one of two sides of an annular groove. Therefore, use of this seal requires the manufacturing of a groove into the shaft. In addition, the ability of this seal to effectively seal a high temperature turbine housing is questionable.
The sealing device of the present invention solves one or more of the problems set forth above.